Ross Curves

Could be okay.  You did not say what trains you run; post war or scale Big Boys/21” passenger cars.  

Good question!  All scale.  Challengers and 21 inch cars.  With that big of a radius, is that a problem?

It might be a little too tight.

Looking at some NMRA recommended practices (see here), they recommend for a radius of about 57" (or about O114 in 3 rail), an adjacent track shouldn't be less than little over 4.5", measuring track-center to track-center. Granted, this table is intended for 2 rail O (and also assumes the largest loco is a Big Boy), but for the wider curves I think it's a helpful guide (eg, if it's too tight for 2 rail, which generally does not tolerate significant overhangs, it is most likely too tight for 3 rail, which is much more lenient in that regard).

The NMRA has a calculator that determines minimum distance between two sections of track to avoid collisions. I can't remember what it's called and I can't find it right now using a quick google search, but if you have the engine/rolling stock, you can take some measurements and the calculator will tell you what they recommend as the minimum spacing. You will need to invest a bit of time getting accurate measurements of your engines and rolling stock (eg, distance between articulation points, etc) to make the most of it, but I think it's handy to have in a digital toolbox.

I would think that 4" spacing might be a little tight.  At our club we had 4.5" spacing with O99 on the inner track and flex track making the outer track, and the VL-BB on the innter track took a string of 21" passenger cars out on the outer track.  That spacing was changed to 5.25"...

Thank you for the responses.  I will go with Atlas flex with a 5.5 to 6 inch gap.  Ross switches (-:

@lionel89 posted:

Good evening, all.  Quick question.  Is it prudent to use Ross 128" diameter curves alongside Ross 120" diameter curves?  Inner loop and outer loop.  Thanks in advance.

60" and 64" radius (O-120/O-128") are considered broad per NMRA standards. If you're running big articulated steam on the inside and full-length passenger cars on the outside, you may get a sideswipe. Everything else, except maybe a Schnabel, should clear.

I have used 5.5" with no issues so I agree with that. My Big Boy will arrive later this year and that will be the real test.

I would recommend Gargraves flex over Atlas flex in terms of what is easier to work with. You might have other reasons for using the Atlas Flex but I just wanted to share that I found it difficult to bend.

In working with Ross sectional track, I have found that it is  a little flexible so it would be easy to make the 120 track form a 118 diameter and the 128 form a 130 radius giving you a full 6 inches center to center which should clear anything, especially at that wide radius.

I agree with others that working with Atlas O flex track is EXTREMELY difficult.  Before you make that decision, you might consider acquiring a piece of Atlas 40 inch flex track to experiment with.

Another way to achieve more spacing is to place a 4 or 5 inch straight in the outer curve.  Most people will not notice that it is there.

Good luck with your decision,

Don

@lionel89 posted:

Thank you for the responses.  I will go with Atlas flex with a 5.5 to 6 inch gap.  Ross switches (-:

Go with 4 inch gap.  Much more realistic!  I have 096 and 089.  I run 21 inch passenger cars.  No problem.  YOUR CURVES ARE HUGE!!!  I've never seen anyone in person with those large curves which will make your 21 inch cars look fabulous!

PS: Atlas flex trak $27 + a section!!!  Gargraves track/Ross Switches BEST!!!  Gargraves flex $12 per section.  USE Gargraves.

With O72 minimum curves and wider on the outside, I went with 5.25 minimum on curves.

Here's a shot of my outer loops; outer track is Ross 128. I don't remember the spacing I used...  I run 21 inch coaches, never a problem, but I don't have a big boy.

FWIW, my Ross curves are 3 1/2 inch spacing center to center on the straights, with 6 inches in the curves.

My fixed-diameter, visible curves are Ross 104/112, hence 4" centerline spacing.  Simulations before construction showed no problems with 21" passenger cars, E-unit diesels, and a NYC 4-8-4 Niagara, my largest steamer.  Since my prototype (NYC) never ran anything larger, I don't expect any problems.  My variable-radius, hidden horseshoe curves taper down to 72/80 at their apexes, at which the track spacing is 5".  Simulations showed no issues with this spacing, either.